I had a crush on a friend who turned out to be gay, and even after learning that he will never feel the same way about me it took me months to get over him. I had become very attached to the idea that we would be together or at least good friends. All I can say is do not reject the way you feel. I constantly went back and forth between saying it didnt mean anything, or it meant everything and I always felt guilty about the way I felt. First just feel and tell yourself it is alright to feel that way! Then, let go of it. This is hard to explain, because it not forcing yourself to not feel that way, its kind of letting it fade. It is a process, it may take time and you have to be kind to yourself if you still have a crush on him after some time.

I still remember the feeling when I finally let go, I had wrote in my journal before I saw him as just a friend,
” ‘the eyes are blind to what is essential only the heart sees clearly’ Today I trust in love… I have felt times when hope was lost and love was denied and it was painful. It is clear to let love and hope guide me because it makes life a beautiful place to live in” and after fully accepting that I felt that way even if it meant nothing for the future, I let go and I stopped thinking of him.
This is just my personal experience, after that point I treated him as a friend again and not a crush.